Conventionally, a network which includes a data processing unit such as a host computer, etc., and a printing device such as a printer, etc., that are connected, wherein image data processed in the data processing unit is sent to the printing device to produce print output is known.
In the network including plural printing devices, various arrangements for appropriately assigning printing jobs requested from the data processing unit to respective printing devices have been proposed. Such arrangements are known, for example, through Japanese Laid-Open Patent Application No. 274098/1993 (Tokukaihei 5-274098) wherein an appropriate printer for a requested printing job is selected among plural printers connected to the network, according a precision of print data, a paper size., etc.
Another arrangement is disclosed in Japanese Laid-Open Patent Application No. 122715/1991 (Tokukaihei 3-122715) wherein each printer is assigned a priority beforehand, and requested printing jobs are assigned according to the priority.
A still another arrangement is disclosed in Japanese Laid-Open Patent Application No. 303475/1993 (Tokukaihei 5-303475) wherein printers connected to the network are divided into groups, and requested printing jobs are assigned in such a manner that a printer in a group processes printing jobs of the paper of the same size as much as possible to reduce the frequency of exchanging sheets.
Recently, a so-called composite digital copying machine which serves both as a copying machine (copy function) for outputting a copied image that is read from a document such as a scanner, etc., and as a printer (print function) for outputting a print of image data sent from an external data processing unit, etc., has been used in practical applications. Furthermore, such attempt that the described composite digital copying machines are connected to a network, and are used both in processing copying jobs and printing jobs has been made.
However, in the conventional arrangement where the composite digital copying machines are connected to the network, the technique of using the composite digital copying machines both as printers and copying machines on a full-scale has not yet been established. Namely, in the conventional arrangement, the composite digital copying machines whose modes are set to either the printing mode or the copying mode beforehand are connected to the network. In such arrangement, when the user desires to alter the ratio in number of the printing devices dedicated to printers to the number of printing devices dedicated to copying machines in the network, a network administrator is required to switch the operation mode.
Therefore, in the case of the network of a large scale, the network administrator must perform troublesome tasks such as monitoring a usage of an entire network, switching an operation mode, etc., thereby presenting the problem of increasing a burden of a network administrator. In addition, for example, in response to an urgent request for a copying job, in the case where an operation mode of the composite digital copying machine set near the user is selected to be the printing device dedicated to printer, the user of the network must look for a printing device that can process a copying job. As described, in the described conventional network, the composite digital copying machines cannot be used on a full-scale.